Catheters have long been used for the treatment of diseases of the cardiovascular system, such as treatment or removal of stenosis. For example, in a percutaneous transluminal coronary angioplasty (PTCA) procedure, a catheter is used to transport a balloon into a patient's cardiovascular system, position the balloon at a desired treatment location, inflate the balloon, and remove the balloon from the patient. Another example of a common catheter-based treatment is the placement of an intravascular stent in the body on a permanent or semi-permanent basis to support weakened or diseased vascular walls, or to avoid closure, re-closure or rupture thereof.
These non-surgical interventional procedures often avoid the necessity of major surgical operations. However, one common problem associated with these procedures is the potential release of debris into the bloodstream that can occlude or embolize downstream vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible for the metal struts of the stent to cut into the stenosis and shear off pieces of atherosclerotic plaque which become embolic debris that can travel downstream from the interventional or surgical procedure and lodge somewhere in the patient's vascular system. Further, pieces of plaque or clot material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become entrained in the bloodstream.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments are dislodged in the circulatory system during vessel treatment. One protection technique includes the temporary placement of an intravascular filter or trap downstream from the treatment site to capture debris before it can reach and embolize smaller blood vessels downstream. The placement of a filter in the patient's vasculature during treatment of a vascular lesion can collect embolic debris in the bloodstream. At the end of the vessel treatment, the filter can be removed along with the captured debris. Such filters typically comprise a filtration membrane, mesh or “basket” having a plurality of pores, each pore being sized to prevent passage of particulate larger than a certain size, e.g., 100-200 microns.
Conventionally, embolic filters are positioned downstream from the treatment device in a location that is distal to the treatment device with respect to the clinician. In such a distal location, the filter may be deployed in a location that does not interfere or interact with the proximally located treatment device. For example, it is known to attach an expandable filter to a distal end of a guidewire or guidewire-like member that allows the filtering device to be placed in the patient's vasculature. The guidewire allows the physician to steer the filter to a location downstream from the area of treatment. Once the guidewire is in proper position in the vasculature, the embolic filter can be deployed to capture embolic debris. Treatment devices then can be delivered to the area of treatment by tracking over the guidewire or guidewire-like member.
However, in some interventional procedures such as heart valve repair or replacement, it may be desirable to deploy an embolic filter in a location that is proximal to the treatment device with respect to the clinician. In such a proximal location, the treatment device may interfere with filter deployment. Thus, a need arises in the art for a filter system particularly suited for use in a valve repair or replacement procedure.